Biomedical Engineering Reference
In-Depth Information
Figure 9.6
Scanning electron micrograph showing the microstructure of PDLLA-
Bioglass-filled composite foam (10 wt% Bioglass) showing interconnected porosity
and bioactive glass particles on the strut surfaces. Scale bar 50
m. (Reprinted with
permission from [10]. Copyright (2003) John Wiley and Sons Ltd.)
μ
need to be fabricated. This pore structure differs considerably from that
achieved by the traditional particulate salt leaching process; in that case
foams exhibit a more isotropic structure with equiaxed pores but much
less interconnectivity. Highly porous tubular scaffolds with oriented
porosity have also been fabricated by exploiting the TIPS process. TIPS-
fabricated PDLLA foams with and without Bioglass additions have been
shown to exhibit mechanical anisotropy concomitant with the TIPS-
induced pore architecture. For comparison, the mechanical properties of
a selection of highly porous scaffolds produced by different methods are
shown in Table 9.4. Inclusion of stiff inorganic bioactive phases gives
slight improvement in the Young's modulus and compression strength
of scaffolds. Section 9.5 will describe in detail poly(DL-lactide)-Bioglass
composite scaffolds developed for bone tissue engineering by TIPS.
9.4.2 Solid Freeform Fabrication/Rapid Prototyping
Solid freeform fabrication (SFF) techniques, such as fused deposition
modelling (FDM), can be used to fabricate highly reproducible scaf-
folds with fully interconnected porous networks. Using 3D digital data
produced by computer axial tomography (CAT) scans or magnetic
resonance imaging (MRI) enables accurate design of the scaffold struc-
ture. In principle, a CAT scan could be taken of healthy bone and
the scan converted into a computer-aided design (CAD) file, which
could be used to drive the SFF machine. The SFF machine would then
